PT&P fabricated variable springs from hot-dipped galvanized carbon steel components and a neoprene coated spring steel coil. P.T.F.E. slide plates are welded to the load flange to reduce frictional forces generated during lateral movement of the supported pipe. Internal guides are also installed to help maintain vertical alignment of all moving components throughout the anticipated thermal deflection cycle. The installed (cold) load is set to 10,413 lb. With a design travel of 0.720” up, the final operating (hot) load will be 8,974 lb. Each spring is equipped with travel stops and went through load testing prior to shipping.

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Piping Technology & Products, Inc. manufactured a variety of F-type variable springs with loads ranging from 526 lb. to 33723 lb. These variable springs are fabricated from a combination of carbon steel and A193-B7 CroMoly steel with A304 stainless steel slide plates. The variable springs are modified to include fully adjustable travel stops. The first purpose of the adjustable travel stops is to aid by distributing the load evenly during the installation process. The second purpose is to allow spring adjustment to any load within the operating range.

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These variable spring hangers were custom designed per customer specifications for a power plant in Turkey. The pipe hanger assembly measures 7′- 6″ long and the diameter of the can measures 12″. The variable spring hanger is capable of 55,137 lb. of hot load and 63,339 lb. of cold load. The assembly allows for 1″ upward travel.

In order to achieve the required spring rate, PT&P utilized a set of stacked coils (5 5/8″ O.D.) nested inside a larger coil. This produced an overall spring rate of 9,235 lb/in. The upper and lower attachments were minimized to fit within the space requirements provided.

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This Type G variable spring was manufactured for a Petrochemical Plant in Mexico. The Type G assembly is formed by welding two standard spring assemblies to the ends of a pair of channels. This type of assembly can accommodate unusually heavy loads, and is especially convenient for avoiding interference in spaces where headroom is limited.

Each spring assembly is loaded per the client’s specification at Piping Technology and Products manufacturing facilities. A travel stop is inserted and strapped in place to maintain the load for the assembly installation. In addition to banding the travel stops, the variables for this project required chained travel stops. The base style (F-Type) variables on this project were also required to have internal guides.

At Piping Technology and Products, Inc. we use PTP-1, PTP-2, PTP-4, PTP-6 and PTP-8 to designate the five standard coil arrangements to increase the working range of travel of variable supports.

Several types of variable supports were made for this particular project. They included Type A, Type B and Type F.

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All of the custom designed variables consist of a single flange with two spring supports in order to meet the customer’s height restrictions. These PTP1-140 Type F variable springs are fabricated from A36 carbon steel with an overall weight of 16,900 lbs. They are designed for upward movement of 0.079″ with a hot load of 4,490 lbs., and a cold load of 4,620 lbs.

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All of the spring components are made of A4150H and carbon steel. Per customer’s request, a two coat epoxy paint was applied to the springs. The Type-A variable spring assemblies measure 22″ x 79″ with an installed load of 45,000 lb., operating load of 56,000 lb., and a downward travel of 5″. The Type-C assemblies measure 22″ x 89″ with an installation load of 38,000 lb., operating load of 47,000 lb., and a downward travel of 5 1/2″. Each spring coil was tested to insure the wire diameter, coil height, and spring rates.

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Piping Technology and Products, Inc. custom designed and manufactured variable springs to be used in conjunction with a rod and clevis assembly for a power plant in West Virginia.  Since the operating loads specified by the customer were greater than the maximum loads for the largest PT&P spring, custom units needed to be built for this application. The springs were fabricated using a large spring coil, normally only used in constant spring assemblies. The spring is 20 1/2″ in diameter and has a standing height of 51″. All components of the pipe hanger assembly were made from carbon steel and were supplied with a hot-dipped galvanized finish. The spring is 20 1/2″ in diameter and has a standing height of 51″.  The rods will be attached to type A variable springs designed to support loads from 850 lbs. to 13,300 lbs. Manufactured from A-36 carbon steel, the rods are 3/4″ to 2″ in diameter and range in length from 68″ to 95″.

To prevent contamination at high temperatures, a non-galvanized finish was applied to the rods per customer’s request. Prior to delivery, a 100% dye-penetrant test was preformed to ensure quality.  The variable springs were tested in the load cell to insure proper operation and also to set the cold load to the specifications as provided by the customer.

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